The weak effect of static, externally imposed, helical fields on fusion product confinement in the DIII-D tokamak

Heidbrink, W. W.; Carolipio, E. M.; Haye, R. J. La; Scoville, J.T.

doi:10.1088/0029-5515/40/5/306

Cited by 5 publications

(4 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[8]. In a study using externally imposed helical fields on DIII-D, no impact on fusion product confinement was observed, consistent with theoretical estimates [9]. In the Auburn torsatron, the effects of rotating, externally imposed magnetic perturbations on ion confinement were consistent with the predictions of intrinsic orbit stochasticity theory [10].…”

Section: Introductionsupporting

confidence: 72%

Simulations of beam ion transport during tearing modes in the DIII-D tokamak

Carolipio¹,

Heidbrink²,

Forest³

et al. 2002

Nucl. Fusion

View full text Add to dashboard Cite

Large coherent MHD modes are observed to reduce the neutral beam current drive efficiency and 2.5 MeV neutron emission in DIII-D by as much as ∼65%. These modes result in large (width w 20 cm for minor radius a ≈ 60 cm), stationary, single helicity magnetic islands, which might cause anomalous deuterium beam ion losses through orbit stochasticity. An analytic estimate predicts that co-going, passing deuterons with E 40 keV become stochastic at island widths comparable to those in the experiment. A Hamiltonian guiding centre code is used to follow energetic particle trajectories with the tearing mode modelled as a radially extended, single helicity perturbation. In the simulations, the lost neutral beam current drive and neutron emission are 35% and 40%, respectively, which is consistent with the measured reductions of 40 ± 14% and 40 ± 10%. Several features of the lost particle distribution indicate that orbit stochasticity is the loss mechanism in the simulations and strongly suggest that the same mechanism is responsible for the losses observed in the experiment.

show abstract

Section: Introductionsupporting

confidence: 72%

Simulations of beam ion transport during tearing modes in the DIII-D tokamak

Carolipio¹,

Heidbrink²,

Forest³

et al. 2002

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

“…For example, the total neutron emission rate (S n ), the neutron emission profile, and the neutron energy spectra are measured in order to understand the global confinement property, the radial density profile, and the velocity space distribution of energetic particles [3]. Time-resolved measurement and time-resolved analysis based on the classical confinement of beam ions and fusion born tritons have been performed to understand the global confinement of energetic ions in deuterium plasmas in tokamaks [4][5][6][7][8][9]. Although the absolute value of DD and DT neutron emissions by these codes are overestimated compared with that obtained by the experiment or with that evaluated by the neutron emission calculation code based on five-dimensional modeling, the code based on the classical beam confinement has an advantage in the low calculation cost (time and memory).…”

Section: Introductionmentioning

confidence: 99%

Time dependent neutron emission rate analysis for neutral-beam-heated deuterium plasmas in a helical system and tokamaks

Ogawa

Isobe

Nishitani

et al. 2018

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

A neutron rate analysis code called the FBURN, based on the classical energetic ion confinement assumption with radial diffusion, is developed for the time-dependent analysis of the total neutron emission rate (Sn) in neutral beam (NB) heated deuterium plasmas. The time trend of Sn evaluated by the FBURN shows good agreement with the Sn measured by the neutron flux monitor on the deuterium operation of the Large Helical Device (LHD). The dependence of Sn on line-averaged electron density (ne_avg) has a peak at ne_avg of around 2.5×10 19 m -3 in both experiment and calculation. Here, the absolute value of Sn evaluated by calculation agrees with that obtained in experiments within a factor of two. Time trend analysis of Sn in an electron cyclotron heated plasma with a short pulse neutral beam injection is performed. The analysis shows that the diffusion coefficient of co-going transit beam ions is 0.2 to 0.3 m 2 /s. In addition, the diffusion coefficient of helically trapped beam ions decreases from 5 to 3 m 2 /s with the inward shift of the magnetic axis position. Time-resolved analysis of the triton burnup experiment shows that the diffusion coefficient of tritons is around 0.15 m 2 /s. It is found that the diffusion coefficients of the beam and tritons are of a similar value as obtained in JT-60U.The trend of the triton burnup ratio on the ne_avg calculated by the FBURN agrees with the experiments. The results suggest that the decrease of the triton burnup ratio with the increase of ne_avg is due to the shorter slowing down time of tritons by the decrease of the electron temperature, and the increase of the triton burnup ratio with the increase of ne_avg 2 is due to the diffusion of tritons. Time trend analysis of Sn in the Korea Superconducting Tokamak Advanced Research (KSTAR) and the Experimental Advanced Superconducting Tokamak (EAST) plasmas with a short pulse NB injection is performed.The time trend of Sn is successfully reproduced by the FBURN.

show abstract

“…33 The maximum amplitude of the imposed perturbation was limited to ;9 G because larger fields caused the plasma to disrupt. These fields, which are an order of magnitude smaller than the tearing-mode field studied in Ref.…”

Section: Iiib Effect Of Helical Fields and Low-frequency Mhdmentioning

confidence: 99%